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The 2026-07-28 MCP specification

Author
Model Context Protocol maintainers
Published
21 May 2026
Added
4 October 2026
Original
https://blog.modelcontextprotocol.io/posts/2026-07-28-release-candidate/

Summary

The release candidate post for the 2026-07-28 MCP specification, described by the maintainers as the largest revision since launch. The final spec was published on 2026-07-28 (https://blog.modelcontextprotocol.io/posts/2026-07-28/).

Key points

  • Stateless core: the initialize handshake, Mcp-Session-Id, and protocol sessions are removed.
  • Roots, Sampling, and Logging are deprecated with a 12-month removal window.
  • New MCP Apps: server-rendered HTML interfaces shown in sandboxed iframes.
  • Tasks redesigned as an opt-in extension for long-running work.
  • Formal extensions framework and deprecation policy.
  • Authorization hardened (issuer validation, OpenID Connect alignment).
  • Transport: Mcp-Method and Mcp-Name headers for routing, cacheable tools/list, W3C trace context, and multi-round-trip requests instead of SSE streams.

Why it matters

Servers and clients built on earlier versions need changes; the stateless design makes MCP servers much easier to host behind ordinary load balancers.